Torque amplifier



March 5, 1946. w. r ucKEk ETAL' TORQUE AMPLIFI Filed Dec. 18, 1941 2Sheets-Sheet 1 Wham-c515, 1946. w. R. TUCKER ET AL. 2,395,979

TORQUE AMPLIFIER I 7 Filed Dec. 18, 1941 2 Shets-Sheet 2 nnowcvsPatented Mar. 5, 1946 UNITED STATES PATENT OFFICE TORQUE AMPLIFIER IWarren R; Tucker, Dayton, and George A. Waldie, Franklin, Ohio,assignors to The Hydraulic Development Corp. .Inc., Mount Gilead, Ohio,a

corporation of Delaware Application December 18, 1941, Serial No.423,488

Claims.

a direct relation, such for example as synchronization in time or rate,between the operation of the initiating impulse and the controlled forceof considerably greater magnitude. For example, in the operation of anairplane it may be desired to move one or more control surfaces from thepilots position and depending on the size of the surface and thedirection of movement, the force required at the control surface may beextremely large and yet the manually applied initiating force at thepilots seat may be relatively small.

Again, in the case of direction-finding apparatus in an airplane, as forexample when the devices are set for automatic pilot and the airplane isriding a radio beam, a direct mechanical connection may be desiredbetween the radio compassand the rudder. The mechanical energy availableat the compass is usually diminutive, whereas the energy required tomove the rudder is exceedingly large.

In still other applications, for example in the automatic control of airconditioning or ventilating systems by a' master indicator, a suitableform of connection other than electrical may be desired between theindicator and the controlled air conditioning or ventilating elements.

The primary object of the present invention is to provide a torqueamplifier for converting small rotary efforts into powerful mechanicaleffects through the use of fluid pressure.

Another object is to provide atorque amplifier of the type referred to,in which there is a direct relation either in terms of speed or rate ofmovement, between the controlling efiort and the controlled source ofhydraulic power.

A further object is to provide a torque amplifier in which synchronismin speed or rate of movement. is achieved between the initial rotaryeffort and the final mechanical movement of considerable power.

Other objects are to control the admission of pressure fluid to ahydraulic motor with apparatus which requires only a relatively smallcontrol effort; to provide a torque amplifier capable of being employedwith ordinary indicating devices of instruments which respond to changesof electrical, mechanical or pneumatic energy to increase the power ofthe indicating instrument to a point sufficient to control remotelypositioned devices or control surfaces.

The final and more general object is to provide a mechanical relay whichcan not only translate movements of low or diminutive power at the inputinto corresponding movements of high power at the output, but has aninexpensive construction and is constituted of such few parts that itsoperation is exceedingly dependable.

These objects are attained, in brief, by combining an improved form offollow-up or servo-valve with a hydraulic motor in such a way andmechanically connecting the units so that even the smallest rotaryeifort exerted at the servo-valve will cause the hydraulic motor toperate either.

at the same speed as the rotary effort or at any proportionate-speed.

In the drawings! I Figure 1 is a vertical longitudinal section of animproved servo-valve which may be employed for carrying out the aboveobjects. In this figure the shafts andthe valve member are shown inelevation.

Figure 2 is a transverse sectional view taken I along the line 2-2 inFigure 1.

Figure 3 shows a hydraulic system in which the improvedservo-valve'illustrated in Figure 1 is connected with a fluid motor forperforming work.

Figure 4 is an enlarged persmctive valve member shown in Figure 1.

Figure 5 is a diagrammatic view with some of the devices in section,showing the application of the invention to a hydraulic motor of thereciprocatory type. a

Figure 6 is a view, wholly in diagram, of the improved torque amplifier,in which the control is obtained through a device operated com pletelyby electrical energy.

Figure 7 illustrates animproved form of pump which, in certain cases,can be used to advantage in operating the torque amplifier. The casingof view of the the pump is shown in section but the rotor is illustratedin elevation. Figure 8 is a perspective view of one of the casingelements of the pump shown in Figure '7. Referring more particularly toFigures 1 and 2, which show the preferred form of servo-valve employedin the improved torque amplifier, the

adapted to serve as a seat or contact surface for a rotary sleeve 3. Thelatter may be made of the same material as the casing. The opening inthe casing I is closed by a closure plate 4 which rests upon a shim 5,and is bolted in position by the screws 6.

The sleeve 3 terminates at the lower end in a shaft 1, the latterprojecting through an opening 8 in the casing and being journalled inthe ball bearing indicated at 9. The latter also serves as a rotarysupport for the sleeve 3. The upper end of the sleeve is counterbored,as indicated at ID, to receive ball bearings I which rest against ashouldered portion of the closure plate 4. Thus the sleeve 3 issupported at each end by ball bearings and may therefore be readilyrotated. The sleeve may be provided with a number of circumferentiallyextending grooves a, b, c, (1, these grooves having a depth which may beone-half the thickness of the sleeve and may be equidistantly spacedapart. In addition to the grooves, the sleeve is provided with a numberof radially extending openings |2, I3, I4, I 5 (of which four have beenillustrated in Figure 2), these openings being preferably equidistantlyspaced about the sleeve and extending between the lowermost surfaces ofthe grooves to the interior of the sleeve. The casing is provided at oneside with a pair of openings I6, I! which communicate at one end withthe grooves b, d and at the other end are provided with conduits l6, I9.At the opposite side of the casing there is a similar pair of openings20, 2| which communicate at one end with the grooves a, respectively andat the other end lead to the conduits 22 and 23 respectively.

Openings I2 and I4 extend inwardly from groove 12 and openings l3 and I5extend inwardly from groove 0. Furthermore, a radial port 80 is providedin sleeve 3 effecting communication between grooves a and 3|, while aradial port 8| effects communication between grooves d and 30, wherebyopening and conduit 22 are in constant communication with groove 3|, andopening I! and conduit l9 are in constant communication with groove 30.

The sleeve 3 is provided with a counterbore 24, extending through thecenter of the sleeve, for receiving a valve rotor 25-which is shown inenlarged form in Figure 4. The bottom of the bore 24 supports a ballbearing 26 on which the rotor is seated, and the latter is rotatablysupported at the top by a ball bearing 21 which surrounds a shaft 28secured to the valve member 25. A washer 29 is interposed between theball .bearing 21 and the lower surface of the closure plate 4. The rotor25 is provided at the end with grooves 30, 3|. There is a pair of slots32, 33, these slots extending along the length of the rotor 25 andoppositely positionedwith respect to the rotor. As shown, the slotscommunicate with the groove 3| but stop short of the groove 30. There isa similar pair of slots 34, 35 displaced 90 degrees from the otherslots, but the slots 34, 35 communicate with the groove and stop shortof the groove 3|. The shaft 1 may be connected to any suitable and wellknown type of fluid motor, indicated at 36 in Figure 3, while the shaft28 which is connected to the rotor, may be coupled to any form ofdevice,

indicated at 31, from which a rotary effort is obtained. This devicemay, for example, be the movable coil of a radio compass, or manuallycontrolled mechanism, in all of which cases it is desired that thiseifort shall be faithfully reproduced but magnified manyfold at theoutput shaft 38 of the fluid motor.

The conduit I9 is connected through tubing 33 to any suitable type 01,pump 46, of which a preferred type will be described in connection withFigures 7 and 8. This pump may be of the constant delivery,non-reversible type because, as will be explained hereinafter, theservo-valve serves to control the direction of the pressure fluid andalso the amount of fluid supplied to the motor load. The fluid, whichmay be oil, is contained in a tank 4| and connected to the pump 40through a pipe 42. The conduit l8 of the servo-valve is connectedthrough conduit 43 to the fluid motor, the other side of the motor beingconnected through conduit 44 which is connected to the conduit 23. Apipe 45 is connected between the tank 4| and the conduit 22. A conduit39a'having therein a pressure relief valve V may connect conduit 39 tosupply tank 4|.

Operation of the combined servo-valve and fluid motor Assume that thepump 40 is actuated, for example, by an electric motor so that pressurefluid is delivered through the tubing 39 to the conduit l9. Assume stillfurther that the shaft 28 has been given a slight turn counterclockwise(Figure 2) so that the slots 34 and 35 of the valve are in completeregister with the openings I2 and M of the sleeve. Slots 32 and 33 willalso be in register respectively with the remaining openings I3 and I5in the sleeve. Under these conditions, fluid under pressure will passfrom conduit |9 through opening grOOVe d, port or ports 8|, groove 30,slots 34 and 35, openings l2 and M and groove b, to opening l6 andthence through conduit It! to motor 36. The fluid then operates toactuate motor 36, the latter exhausting through conduit 44 to opening2|, groove c, slots 32 and 33, groove 3|, port or ports 80, opening 20,and. conduit 22 to supply tank 4|.

Now assume that the valve 25 has been moved counterclockwise (Figure 2)in such a manner that the slots 32 to 35 are sufficiently in registerwith openings I2 to l5 to permit the admission of at least small amountsof fluid to the motor 36. The motor 36 will turn until the sleeve 3 hasbeen given an angular movement suflicient to bring the slots into closedposition as shown at Figure 2. Thus the motor will have turned throughthe same angle of rotation as the valve 25. If the latter were given acontinuous rotation by the device 3'|, the motor 36 would necessarilytend to continuously move the sleeve 3 to follow up the movement ofvalve 25.

Should an increased load be imposed upon motor 36 tending to causesleeve 3 to lag behind valve 25, ports l2 and M are opened further toincrease the pressure acting upon motor 36 and thus increase the torqueexerted thereby to brin its speed to the same as that of valve 25. Thus,within its capacity, the torque developed by motor 36 is proportional tothe load thereon. It is evident that when the shaft -28 is rotated at arelatively low speed the sleeve 3 will faithfully follow the slow speedof the valve 25, and the same thing is true at the higher speeds of thevalve, assuming of course that the load on the motor 36 is notsufficiently high to prevent this automatic synchronizing action.

In order to reverse the fluid motor 36, it is only necessary to rotatethe shaft 28 in the opposite direction. Assume that the valve 25 isrotated sleeve.

the opening I2. Under these conditions pressure fluid is brought to theconduit I9 and will flow around the groove d in the sleeve 3 through theradial ports into groove 38 until it reaches the slots 34, 35. The fluidwill then travel along said slots and will flow through the openings I5,I3 etc. until it reaches the groove c, whereupon it will gain theopening 2| and flow through the tubing 44, into the fluid motor. Thelatter will therefore be actuated in the'oppo'site direction. The tubing43 will now constitute the exhaust conduit,'the fluid passing from theopening I6 into groove b, openings I2 and I 4 into slots 32 and 33 togroove 3|, thence through radial port or ports 80 to groove a to conduit22. From the conduit 22 the fluid is exhausted tothe tank 4|.Consequently, regardless of the direction of rotation of the rotaryinput device 31, the fluid motor will rotate in the same direction, andas stated hereinbefore, at synchronous speed, In case the valve rotor 25will have moved through less than a whole revolution, the sleeve willturn' through the same angle and then come to a stop. Thus, the finalposition of the shaft 38 will be the same, or substantially so, as thatof the valve rotor,

Inasmuch as the pressure fluid reaches-both sides of the valve 25regardless of the direction of rotation of the valve, the latter iscompletely balanced on its circular seat so that little or no frictionis exerted between the valve member and the sleeve. The same thing istrue of the sleeve 3 because, as pointed out hereinbefore, pressurefluid gains access to both sides of the sleeve, regardless of thedirection in which the shaft 28 is rotated. The end thrust of the valveis taken by the frictionless bearings 26, 21, while the ball bearings 9and II serve the same purpose for the Consequently, there is little orno friction between any of the moving parts, or between the rotatingsleeve and the stationary casing I. Any small rotary effort exerted atthe shaft 28 is utilized merely for rotating the shaft because thesleeve 3 is rotated by the much more powerful motor 36. Thus the valve25 merely serves to open and close hydraulic circuits, and this functionis performed most effectivel because when the valve, for example, ismoved to the po. sition shown in Figure 2, the fluid circuits throughthe servo-valve are interrupted so effectively that little or no leakagecan take place even though extremely high fluid pressures are availableat the pump.

It is apparent that the fluid motor may be of any size and thereforeable to exert any amount of power, andyet the control exercised at thedevice 31 is positive and is adapted to any desired speed and utilizingeither direction of rotation. Due to the manner in which the slots 32 to35 cooperate with the radially extending openings I 2 to I5, there ispositively no tendency for the valve 2 25 to be rotated other than atthe shaft 28 when high pressure fluid is being handled by theservovalve. Thus no overrun of rotation is present in either direction,and the fluid motor will rotate through its proper angle of movement,greater or less than a complete revolution, corresponding exactly to themovement of the control device 31. It is apparent that the same rotaryeffects would be obtained if the shaft 1 were connected in any suitablemanner to the rotor 25 instead of'the sleeve. The sleeve would then beconnected to the shaft 28 and become the control member.

Instead of employing a fluid motor which serves to rotate the shaft 38when fluid pressure is applied thereto, it may be desirable to translatethe rotary effort-oi. the control device 31 into a reciprocatorymovement. This modification has been shown in Figure 5, and in this casethe shaft 1 of the servo-valve is provided with a pinion 48 which mesheswith a rack 41. The latter is secured to a piston rod 48, carrying apiston 49 and contained within a cylinder 58. Conduits 5| and 52 aretaken from opposite ends of the cylinder and connected respectively withconduits I8 and 23 of the servo-valve casing I.

The operation of the system shown in Figure 5 is somewhat similar tothat which has been described in connection with Figure 3 except thatwhen the shaft 28 is rotated by the control element 31, fluid pressureis supplied either to the conduit 5| or 52, depending on the directionin which the control element 31 is rotated. Thus the piston 49 becomesdouble-acting, assuming that the element 31 is rotated alternately inopposite directions and the rod 48 is given a reciprocatory movement toperform work. The system shown in Figure 5 is particularly well adaptedfor actuating the control surfaces of an airplane, all

of which move through a limited angle corresponding to the movement ofthe rod 48. One advantage of this system is that the shaft 28 may berotated through quite a number of revolutions and yet the piston 49 willonly have moved through a limited lateral distance, depending on thenumber of teeth ratio between the pinion 46 and the rack 41. It isapparent that if desired a reciprocatory movement initiated, forexample, by the pilot's control stick, may be imparted to the shaft 28in terms of a rotary effort, so that the movements of the control stickwill be exactly synchronized or bear any desired proportionate movementwith respect to the movement of the rod 48. Thus the movement of thecontrol stick from, for example a vertical position to the left, willresult in the rotary movement of the shaft 28 in a particular direction,and a movement of the control stick to the right will cause the shaft 28to move in'the op site direction, causing correspondingly oppositemovements of the piston 49.

In Figure 6 another modified system is shown, employing the improvedtorque amplifier. The servo-valve, fluid motor, pump, tank andinterconnecting conduits may be similar to those shown in Figure 3 andfor that reason bear the same reference numerals. However, in thisfigure the shaft 28 is rotated by a synchronous motor, indicated at 53,which may be of very small size and either energized directly orcontrolled in any suitable and well known manner by a vacuum tubeoscillation generator 54. The oscillations developed by the generatormay be controlled by a dial indicated at 55, and the output of thegenerator is taken through the conductors 56, either directly to thefield winding of the synchronous motor 53 or any other control windingof the motor. The synchronous motor, for example, may be of a size notmuch greater than that used in an ordinary electric clock, which it hasbeen found is more than sufficient to operate the valve 25. Thusbyturning the dial 55, which controls the frequency of the oscillationsdeveloped at 54, the .speed of the shaft 28 is controlled, which inturn, controls the speed of the fluid motor 36, as'has been describedhereinbefore. Any suitable form of reduction gearing, indicated by therectangle 51, be-

tween the synchronous motor 53 and the servotransmissions." so that thesynchronous motor 58 may be operated at constant synchronous speed andthe speed of the shaft 28 can be controlled at the variable transmission51. It is apparent that if desired the oscillation generator 54 and thesmall synchronous motor 58 may be replaced, for example, by the movablecoil of a radio com- P 5. direction and at such a speed comparable tothe movement of the compass coil.

In Figures 7 and 8 there is illustrated an improved form of pump, whichit has been found operates extremely satisfactorily in connection withthe torque amplifier including the improved servo-valve shown in Figurel. However, it will be understood that our invention is not limited tothe particular form of pump illustrated, but the latter represents adiminutive, large-output pump of the rotor type which is particularlywell suited to the valve-opening and closing operations of the improvedservo-valve. As illustrated, this pump consists essentia.ly of aplurality of end blocks 58, 59 which are spaced apart by an intermediateblock 50, the three blocks being secured in position by bolts, of whichonly the openings 50' are indicated in Figure 8. The intermediate block50 is provided with a centrally disposed opening this opening beingcurved along its depth for reasons which will be apparent when theimpeller construction has been described. The opening 5| constitutes apumping chamber which has'been designated 62.

The blocks 58, 59 are provided with countersunk openings which areadapted to receive the ball bearings 53, 54 for supportingthe rotorshaft 55. The rotor is formed essentially of a spherical portion 55which is seated in spherically curved surfaces formed in the blocks 58,59. This spherical portion of the rotor is provided with an outwardlyextending annular ring 51, the diameter of which is such as to cause thering snugly to fit the opening 5|. The ring 51 is provided about itsperiphery with radially extending slots, and each slot carries a vane orblade 58 in a slidable fit. These blades are adapted to move withintheir slots in a direction parallel to the direction of the shaft 65,andat all times make contact in which case the shaft 88 will turn in a.

grooves through suitable conduits, of which one 15 has.

in the block 59 but positioned diagonally with respect to one another.This pair of grooves, which obviously will be positioned on oppositesides of thelongitudinal axis of the pump, are connected together in anysuitable manner through passageways, of which only one designated I4,has been vided in the blocks 58 and '59. As in the case of the pair ofsuction slots 13, the pair of pressure to one another on opposite sidesof the longitudinal axis of the pump and are connected'toge'ther beenillustrated in Figure 8. The conduit 15 comwith the active surfaces ofthe pumping chamber 52 as the impeller is rotated.

In order to provide pressure and exhaust chambers within the pump theblock 58, 59 are given tapered surfaces, as indicated at 59 and 10,respectively, the intermediate block being also tapered as indicated, sothat the line of joining between the various blocks will extenddiagonally with respect to the vertical plane. That portion of theactive surfaces of the blocks 58, 59 contained within the pumpingchamber 52 is given an additional taper, as illustrated, in order thatthe upper right-hand edge and the lower left-hand-edge of the ring 5'!shall bear against a vertical surface. indicated at H. It is apparentthat the spaces to the left of the upper edge of the ring 51 and to theright of the lower edge of said ring constitute suction chambers, sothat as the rotor 56 is rotated the vanes 58 will tend to move the fluidcollected in these spaces around to that position at which there is nospace between the ring 51 and the blocks 58, 59, i. e. at the positionsindicated at H. Consequently, these positions represent those placeswhere pressure is introduced into the Communication between thesesuction chambers and an inlet port 12 is obtained through a pair ofarcuate grooves 13, one of which is proided in the block 58 and theother is provided municates with the pressure-port H. The suction port12 andthe pressure port Tl are brought out through conduits l2 and 39,respectively (see Fi ure 3). It is apparent that as the rotor 55 isrotated the vanes 58 are caused to move in their slots to follow theshape of the pumping chamber 52, and the oil or other fluid presentwithin the pumping chamber is caused to be forced by the operation ofthe vanes 58, into the pressure grooves 15. The rotor, therefore, serveto draw fluid into the pumping chamber through the port 12, into thepair of grooves 13 and out through the. pair of pressure grooves 15.into th port 11.

As the shaft 55 is rotated faster the output of the pump becomesgreater. The pump shown in Figures '7 and 8 is characterized by a largeoutput at relatively high pressures for a given size of ump so that apump of this character, particularly when made of light metal, is wellsuited to provide the necessary pressure fluid for operating the torqueamplifiers shown in Figures 3, 5 and 6. However, it will be understoodthat any other type of pump in which a continuous flow of fluid isavailable may be employed.

From the foregoing it is evident that we have invented a new and usefulform of torque amplifler, in which the servo-valve shown in Figure 1,

the fluid motor and the pump shown in Figures 7 i and 8 all cooperate inan eflicient manner toprovide a system in which a relatively smallcontrolling force can control a great hydraulic force represented by thefluid motor 35; and the operation is such that a high degree ofsynchronism is obtained between the rotary controlling force and thecontrolled force. This controlling force may be exercised either bymanual operation or by an electrical instrument, or by a machine or anyother kind of mechanism. This small controlling force may constitute atiming device, exemplified in Figure 6 as a synchronous motor 53energized by the control oscillator 54. The servo-valve I, in effect,constitutes a fluid distributor valve which is controlled by the timingdevice in such a way that the oscillator 54 determines the speed of thepowerful hydraulic motor 35. Thus the latter is controlled accurately bythe use of an extremely small controlling force, due to theinterposition of the servo-valve or distributor l.

The pump shown in Figure '7 represents a type which provides pressurefluid of a character most suitable for control by the servo-valve shownin Figure 1, and to that extent constitutes a complementary unit of theservo-valve in obtaining the optimum results from the hydraulic systemsdisclosed in Figures 3, 5 and 6. This pump is intended to be rotated atfast speeds, and not- 'I5 is positioned diagonally with'respect tion 01'said otor eing connected'torotate said v withstanding its relativelysmall size has a large sleeve, and means for controlling the speed ofoutput compared with the volumetric size of the a pump. The servo-valvei is also of the rotary type and would normally be operated atrelatively fast speeds, similar to the pump, so that when the variouspassageways through the servo-valve have an area to accommodate the fulloutput off, the pump, this output may be transmitted through 1 theservo-valve without the slightest throttling eflect. Thus the pump andthe servo-valve operate unusually well together since both of thesedevices are of the same general type, in that both operate on the rotaryprinciple and both are'capable of being'operated at relatively fastspeeds; and one device-can accommodate the entire output of the otherdevice when full openvalve conditions at the servo-valve are required.However, it will be understood that the servovalve I may be suppliedwith pressure fluid,'if desired, from othertypes of pumps than that.

shown in Figure 7, but the point is made that this particular type ofpump operates exceedingly satisfactorily with the rotary type ofservo-valve disclosed herein.

It will be understood that we desireto comprehend within our inventionsuch modifications as come within the scope of the claims.

Having thus fully described our invention, what we claim as-new anddesire to secure by Letters Patent is: I

1. A torque amplifier comprising, in combination, a rotary servo-valveand a rotary hydraulic motor supplied with fluid from said servo-valve,said servo-valve including a rotor and a surrounding rotary sleeve, saidrotor and sleeve having passageways therein so'arranged that when therotor is rotated relatively to the sleeve the said passageways come intoregister to permit pressure fluid to pass through the servo-valve, themovable portion of said motor being connected to rotate said sleeve, andmeans for controlling the speed of movement of said rotor whereby whenthe rotor is rotated pressure fluid is supplied to the motor to causethe sleeve to rotate through the same angular movement at the same rateas that of the rotor, said means comprising a synchronous motorconnected to rotate said rotor and variable frequency generator forsupplying current thereto.

2. A torque amplifier comprising. in combination, a rotary servo-valveand arotary hydraulic motor supplied with fluid from said servo-valve,

said valve including a rotor and a surrounding' rotary sleeve, saidrotor and sleeve having pasmovement of said rotor whereby when the rotorI generator supplying current thereto whereby the speed of rotation 01'the rotor is varied and the rate of movement of the fluid motor iscorre- Y .spondingly controlled.

,3."A-'torque amplifier comprising, incombination, a'rotary servo-valveand a "rotary reversible hydraulic motor suppiied'with fluid from saidservo-valve, said servo-valve including a rotor and a surrounding rotarysleeve, said rotor and I sleeve having passageways therein so arrangedthat when the rotor is rotated relatively to the sleeve in eitherdirection from a normally closed position the said passageways come intoregister to permit pressure fluid to pass through the sageways thereinso arranged that when the rotor is rotated relatively tothe, sleeve thesaid passageways come into register to permit pressure fluid to passthrough the valve, the rotating porservo-valve to rotate said motor in acorrespond-- ing direction,'said .motor being .connected to rotatesaidsleeve toward said normal position, and means for initiating movement ofsaid rotor whereby when the rotor is rotated, pressure fluid is suppliedto themotor to cause the sleeve to rotate through the angular distanceas the movement of the rotor, said means comprising a rotary powerdevicewhich operates at constant speed and variable speed transmissionmechanism interposed between said device and said sleeve.

' 4. In a torque amplifier, a timing means, a hydraulic power circuitcontrolled and synchronized by the timing means, means for controllingthe hydraulic fluid flow by said timing means, and a reversible rotaryhydraulic motor in said circuit and having a power output shaftconnected to said aforementioned controlling means associated with thetimingmeans for timing and controlling the fluid flow, whereby thetiming, means controlsthe synchronous movement of the motor as actuatedby said hydraulic circuit.

5. In a torque amplifier, a timing means, a

hydraulic power circuit controlled and synchronized by the timing means,means for controlling the hydraulic fluid flow in said circuit, and a 1reversible rotary hydraulic motor' in said circuit and having 'a poweroutput shaft connected to said aforementioned controlling meansassociated with said timing means for timing and controlling the fluidflow, whereby the timing means controls the synchronous movement orthe'motor as actuated by said hydraulic circuit.

WARREN R. TUCKER. .GEORGE A.

